1. Field of the Invention
The present invention relates to an equipped forced-convection housing unit for a rotating-anode X-ray tube as applicable to the general field of radiology and in particular to X-ray devices involving intensive production of X-radiation.
2. Description of the Prior Art
In X-ray tubes, the production of X-radiation is obtained by deceleration of electrons in the target material provided at the anode. This results in considerable heating of the target and of the entire anode, since approximately 99% of the injected energy is converted to heat.
By reason of the vacuum established within the X-ray tube, the greater part of the heat stored within the anode is removed by radiation through the envelope of the X-ray tube. The zones nearest the anode are particularly exposed to high temperatures. In order to avoid excessive local increases in temperature, it is therefore necessary to carry out a heat transfer operation in many cases of intensive use, as in vascular scannography, tomography, and so on. Failing this heat transfer, such local temperature rises would be liable to cause damage to the X-ray tube itself as well as certain components which are contained within a protective housing together with the X-ray tube.
The assembly formed by said housing which contains the X-ray tube is known as an equipped housing. As a general rule, the X-ray tube is immersed in a fluid with which the housing is filled. The fluid is usually oil.
The natural convection of the fluid as a result of the temperature gradient is often insufficient to transfer heat and to prevent the formation of very-high-temperature hot spots. In order to remedy this insufficiency, a known practice consists in producing forces convection or, in other words, causing the fluid to circulate under the action of an outside agency. This external action is usually produced by a pump placed outside the housing in series with a duct for the injection of the fluid and a duct for the discharge of the fluid. In order to cool the fluid which is reinjected into the housing, a heat-exchange device is usually inserted in this circulation system which is located outside the housing.
The equipped housing is a moving element of an X-ray device, and the bulk of an external pump for the forced circulation of fluid constitutes a considerable hindrance. This bulk is increased even further by the cables for supplying current to the pump motor. Another drawback lies in the fact that these pumps require a specific electric supply. It should be added that this pump is liable to increase in bulk to an appreciable extent according to the nature of the fluid by reason of the degree of fluid-tightness to be provided for the cooling circuit. In this case the pumping section proper has to be driven by means of a magnetic coupling. Fluid-tightness as used in this context is understood to mean air-tightness, since the coolant fluid (oil) must be absolutely free from bubbles in order to prevent any breakdown at high voltage.